U.S. patent application number 13/341797 was filed with the patent office on 2013-07-04 for apparatus having double phase-matched configuration for reducing magnitude of intermodulation products.
This patent application is currently assigned to Avago Technologies Wireless IP (Singapore) Pte. Ltd.. The applicant listed for this patent is Paul Bradley, David A. Feld, Won Kyu Kim. Invention is credited to Paul Bradley, David A. Feld, Won Kyu Kim.
Application Number | 20130169378 13/341797 |
Document ID | / |
Family ID | 47682552 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130169378 |
Kind Code |
A1 |
Kim; Won Kyu ; et
al. |
July 4, 2013 |
APPARATUS HAVING DOUBLE PHASE-MATCHED CONFIGURATION FOR REDUCING
MAGNITUDE OF INTERMODULATION PRODUCTS
Abstract
An apparatus includes: a first apparatus port receiving a first
signal having a first frequency; a second apparatus port outputting
the first signal having the first frequency; a first passive device
connected between the first and second apparatus ports; a second
passive device connected between the first and second apparatus
ports; a plurality of phase shifters each providing a corresponding
phase shift, wherein at least one of the phase shifters provides
its phase shift in a first signal path between the first and second
apparatus ports through the first passive device, and wherein at
least another phase shifter provides its phase shift in a second
signal path between the first and second apparatus ports through
the second passive device. The phase shifts are selected to cancel
an upper or lower intermodulation product between the first signal
and a second signal having a second frequency received at the
second apparatus port.
Inventors: |
Kim; Won Kyu; (Seoul,
KR) ; Feld; David A.; (Newark, CA) ; Bradley;
Paul; (Los Altos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kim; Won Kyu
Feld; David A.
Bradley; Paul |
Seoul
Newark
Los Altos |
CA
CA |
KR
US
US |
|
|
Assignee: |
Avago Technologies Wireless IP
(Singapore) Pte. Ltd.
Singapore
SG
|
Family ID: |
47682552 |
Appl. No.: |
13/341797 |
Filed: |
December 30, 2011 |
Current U.S.
Class: |
333/126 ;
333/132 |
Current CPC
Class: |
H03H 7/46 20130101; H03H
9/70 20130101 |
Class at
Publication: |
333/126 ;
333/132 |
International
Class: |
H01P 5/12 20060101
H01P005/12 |
Claims
1. An apparatus, comprising: a first apparatus port configured to
receive a first signal having a first frequency; a second apparatus
port configured to output the first signal having the first
frequency; a first passive device connected between the first and
second apparatus ports; a second passive device connected between
the first and second apparatus ports; a plurality of phase shifters
each configured to provide a corresponding phase shift, wherein at
least one of the phase shifters is configured to provide its
corresponding phase shift in a first signal path between the first
and second apparatus ports through the first passive device, and
wherein at least another of the phase shifters is configured to
provide its corresponding phase shift in a second signal path
between the first and second apparatus ports through the second
passive device, wherein the phase shifts are selected to cancel one
of an upper or lower intermodulation product between the first
signal, and a second signal having a second frequency received at
the second apparatus port.
2. The apparatus of claim 1, wherein the phase shifts are selected
to cancel one of an upper or lower third order intermodulation
product between the first signal and the second signal.
3. The apparatus of claim 1, wherein the phase shifts are selected
to cancel one of an upper or lower N.sup.th order intermodulation
product between the first signal and the second signal, where N is
an odd number greater than 3.
4. The apparatus of claim 1, wherein the first and second passive
devices each have a corresponding first device port and a
corresponding second device port, and wherein the plurality of
phase shifters are configured to provide: a first phase shift
between the first apparatus port and the first device port of the
first passive device; and a second phase shift between the second
apparatus port and the second device port of the second passive
device.
5. The apparatus of claim 4, wherein the first and second phase
shifts are each approximately +90 degrees or -90 degrees at the
first frequency.
6. The apparatus of claim 4, wherein the first and second phase
shifts are each approximately +45 degrees or -45 degrees at the
first frequency.
7. The apparatus of claim 1, wherein the first and second passive
devices each have a corresponding first device port and a
corresponding second device port, and wherein the plurality of
phase shifters are configured to provide: a negative phase shift of
a defined phase angle at the first frequency between the first port
of the apparatus and the first device port of the first passive
device; a positive phase shift of the defined phase angle at the
first frequency between the first port of the apparatus and the
first device port of the second passive device; a positive phase
shift of the defined phase angle at the first frequency between the
second port of the apparatus and the second port of the first
passive device; and a negative phase shift of the defined phase
angle at the first frequency between the second port of the
apparatus and the second port of the second passive device.
8. The apparatus of claim 7, wherein the defined phase angle is
approximately 45 degrees.
9. The apparatus of claim 7, wherein the defined phase angle is
approximately 22.5 degrees.
10. The apparatus of claim 1, wherein each of the first and second
passive devices is a filter.
11. The apparatus of claim 1, wherein the first and second passive
devices have approximately the same S-parameters as each other.
12. The apparatus of claim 11, wherein the apparatus has
S-parameters which are approximately the same as the S-parameters
of the first and second passive devices.
13. The apparatus of claim 1, wherein the first passive device and
the second passive device are configured to apply a same phase
shift as each other at the first frequency.
14. The apparatus of claim 1, further comprising a transmit
amplifier coupled to the first port of the apparatus and configured
to provide the first signal to the first port of the apparatus.
15. The apparatus of claim 14, further comprising an antenna
coupled to the second port of the apparatus and configured to
receive the first signal from the second port of the apparatus.
16. The apparatus of claim 1, further comprising at least one
circulator connected between at least one of the phase shifters and
at least one of the first and second apparatus ports.
17. The apparatus of claim 1, further comprising at least one power
splitter/combiner connected between at least one of the phase
shifters and at least one of the first and second apparatus ports,
wherein the splitter/combiner is configured to split a single
signal path into two signals paths such that in a reverse direction
a differential mode is absorbed.
18. An apparatus, comprising: a first apparatus port configured to
receive a first signal having a first frequency; a second apparatus
port; a third apparatus port configured to output the first signal
having the first frequency and to receive a second signal having a
second frequency, wherein the second apparatus port is configured
to output the second signal having the second frequency; first,
second, third, and fourth passive devices, each having a
corresponding first device port and a corresponding second device
port, wherein the second device ports of the first and third
passive devices are connected together with a first impedance
matching device and the second device ports of the second and
fourth passive devices are connected together with a second
impedance matching device, a plurality of phase shifters each
configured to provide a corresponding phase shift, wherein at least
one of the phase shifters is configured to provide its
corresponding phase shift in a first signal path between the first
and third apparatus ports through the first passive device, wherein
at least another of the phase shifters is configured to provide its
corresponding phase shift in a second signal path between the first
and third apparatus ports through the second passive device,
wherein still another of the phase shifters is configured to
provide its corresponding phase shift in a third signal path
between the second and third apparatus ports through the third
passive device, and wherein yet another of the phase shifters is
configured to provide its corresponding phase shift in a fourth
signal path between the second and third apparatus ports through
the fourth passive device; wherein the phase shifts are selected to
cancel one of an upper or lower intermodulation product between the
first signal, and a third signal having a third frequency received
at the third apparatus port.
19. The apparatus of claim 18, wherein the phase shifts are
selected to cancel one of an upper or lower third order
intermodulation product between the first signal and the second
signal.
20. The apparatus of claim 18, wherein the phase shifts are
selected to cancel one of an upper or lower N.sup.th order
intermodulation product between the first signal and the second
signal, where N is an odd number greater than 3.
21. The apparatus of claim 18, wherein the first, second, third and
fourth passive devices each have a corresponding first device port
and a corresponding second device port, and wherein the plurality
of phase shifters are configured to provide: a first phase shift
between the first apparatus port and the first device port of first
passive device; a second phase shift between the second apparatus
port and the first device port of third passive device; and a third
phase shift between the second impedance matching element and third
apparatus port, wherein the first phase shift, second phase shift,
and third phase shift are all approximately equal to each
other.
22. The apparatus of claim 21, wherein the first, second and third
phase shifts are each approximately +90 degrees or -90 degrees at
the first frequency.
23. The apparatus of claim 21, wherein the first, second, and third
phase shifts are each approximately +45 degrees or -45 degrees at
the first frequency.
24. The apparatus of claim 18, wherein the first, second, third,
and fourth passive devices each have a corresponding first device
port and a corresponding second device port, and wherein the
plurality of phase shifters are configured to provide: a positive
phase shift of a defined phase angle at the first frequency between
the first apparatus port and the first device port of first passive
device; a negative phase shift of the defined phase angle at the
first frequency between the first apparatus port and the first
device port of second passive device; a positive phase shift of the
defined phase angle at the first frequency between the second
apparatus port and the first device port of third passive device; a
negative phase shift of the defined phase angle at the first
frequency between the second apparatus port and the first device
port of fourth passive device; a negative phase shift of the
defined phase angle at the first frequency between the first
impedance matching device and the third apparatus port; and a
positive phase shift of the defined phase angle at the first
frequency between the second impedance matching device and the
third apparatus port.
25. The apparatus of claim 24, wherein the defined phase angle is
approximately 45 degrees.
26. The apparatus of claim 24, wherein the defined phase angle is
approximately 22.5 degrees.
27. The apparatus of claim 18, further comprising at least one
circulator connected between at least one of the phase shifters and
at least one of the first, second and third apparatus ports.
28. The apparatus of claim 18, further comprising at least one
power splitter/combiner connected between at least one of the phase
shifters and at least one of the first, second and third apparatus
ports, wherein the splitter/combiner is configured to split a
single signal path into two signals paths such that in a reverse
direction a differential mode is absorbed.
29. The apparatus of claim 18, wherein the first and second passive
devices are transmit filters, and the third and fourth passive
devices are receive filters.
30. The apparatus of claim 18, wherein the apparatus is a filter, a
duplexer, or a quadraplexer with differential receive ports.
31. The apparatus of claim 18, wherein the apparatus further
comprises: a fourth apparatus port; and fifth and sixth passive
devices each having a corresponding first device port and a
corresponding second device port, wherein the second device port of
the fifth passive device is connected to the first impedance
matching device, and wherein the second device port of the sixth
passive device is connected to the second impedance matching
device.
32. The apparatus of claim 31, further comprising: a first pull
down device connected to the first impedance matching device, and a
second pull down device connected to the second impedance matching
device, wherein the first and second pull down devices reduce a
voltage of the third signal at the third frequency at the second
device ports of the first and second devices.
33. The apparatus of claim 31, wherein the plurality of phase
shifters are configured to provide: a first phase shift between the
first apparatus port and the first device port of first passive
device; a second phase shift between the second apparatus port and
the first device port of third passive device; a third phase shift
between the second impedance matching element and third apparatus
port; and a fourth phase shift between fourth apparatus port and
the first device port of the fifth passive device, wherein the
first phase shift, second phase shift, third phase shift, and
fourth phase shift are all approximately equal to each other.
34. The apparatus of claim 33, wherein the first, second and third
phase shifts are each approximately +90 degrees or -90 degrees at
the first frequency.
35. The apparatus of claim 33, wherein the first, second, and third
phase shifts are each approximately +45 degrees or -45 degrees at
the first frequency.
36. The apparatus of claim 33, further comprising at least one
circulator connected between at least one of the phase shifters and
at least one of the first, second, third and fourth apparatus
ports.
37. The apparatus of claim 33, further comprising at least one
power splitter/combiner connected between at least one of the phase
shifters and at least one of the first, second, third and fourth
apparatus ports, wherein the splitter/combiner is configured to
split a single signal path into two signals paths such that in a
reverse direction a differential mode is absorbed
38. The apparatus of claim 31, wherein the plurality of phase
shifters are configured to provide: a positive phase shift of the
defined phase angle at the first frequency between the first
apparatus port and the first device port of first passive device; a
negative phase shift of the defined phase angle at the first
frequency between the first apparatus port and the first device
port of second passive device; a positive phase shift of the
defined phase angle at the first frequency between the second
apparatus port and the first device port of third passive device; a
negative phase shift of the defined phase angle at the first
frequency between the second apparatus port and the first device
port of fourth passive device; a negative phase shift of the
defined phase angle at the first frequency between the first
impedance matching device and the third apparatus port; a positive
phase shift of the defined phase angle at the first frequency
between the second impedance matching device and the third
apparatus port; a positive phase shift of the defined phase angle
at the first frequency between the fourth apparatus port and the
first device port of fifth passive device; a negative phase shift
of the defined phase angle at the first frequency between the
fourth apparatus port and the first device port of sixth passive
device.
39. The apparatus of claim 38, wherein the defined phase angle is
approximately 45 degrees.
40. The apparatus of claim 38, wherein the defined phase angle is
approximately 22.5 degrees.
41. The apparatus of claim 38, further comprising at least one
circulator connected between at least one of the phase shifters and
at least one of the first, second, third and fourth apparatus
ports.
42. The apparatus of claim 38, further comprising at least one
power splitter/combiner connected between at least one of the phase
shifters and at least one of the first, second, third and fourth
apparatus ports, wherein the splitter/combiner is configured to
split a single signal path into two signals paths such that in a
reverse direction a differential mode is absorbed.
43. The apparatus of claim 31, wherein the first and second passive
devices are transmit filters, the third and fourth passive devices
are receive filters, and the fifth and sixth passive devices are
receive filters operating in a different frequency band from first
through fourth filters.
44. The apparatus of claim 31, wherein the first, third and fifth
passive devices form a first quadraplexer, and wherein the second,
fourth and sixth passive devices form a second quadraplexer.
45. The apparatus of claim 44, wherein the first and second
quadraplexers have approximately the same S-parameters as each
other.
46. The apparatus of claim 45, wherein the apparatus has
S-parameters which are approximately the same as the S-parameters
of the first and second quadraplexers.
47. The apparatus of claim 18, wherein the first and third passive
devices form a first duplexer, and wherein the second and fourth
passive devices form a second duplexer.
48. The apparatus of claim 47, wherein the first and second
duplexers have approximately the same S-parameters as each
other.
49. The apparatus of claim 48, wherein the apparatus has
S-parameters which are approximately the same as the S-parameters
of the first and second duplexers.
Description
BACKGROUND
[0001] Intermodulation, or intermodulation distortion (IMD), is a
multi-tone distortion product that results when two or more signals
are present at the input of a non-linear device. In such a device,
if the applied signals are pure tone frequencies, then
intermodulation products will be generated by the system and can be
found at the sum and difference frequencies of the originally
applied frequencies. More generally intermodulation products will
be found at nF0+mF1+pF2+ . . . , where n, m, and p, . . . are
integers, and F0, F1, F2, . . . are the applied frequencies.
[0002] Intermodulation products can be a significant problem for
many electronic systems, particularly communication systems.
[0003] FIG. 1 depicts an example for illustrating intermodulation
products being generated by a mixing operation of a passive
two-port device 100.
[0004] In this document, a passive device is understood to refer to
a device that exclusively includes passive components such as
resistors, capacitors, inductors, signal traces, crystals, acoustic
wave elements (including surface acoustic wave (SAW), bulk acoustic
wave (BAW), and film bulk acoustic wave (FBAR) devices, etc. A
passive device as described herein does not include active or gain
components, such as amplifiers, transistors, etc.
[0005] As illustrated in FIG. 1, passive device 100 receives an
input signal x(t) having a corresponding frequency domain
representation X(f) and outputs from an output port 105 an output
signal y(t) having a corresponding frequency domain representation
Y(f).
[0006] In general, X(f) may include substantial components at
several different frequencies and/or over a range of frequencies,
but for simplification of explanation, it will be assumed for the
remainder of this discussion that that X(f) is essentially a single
frequency signal at a first frequency F1.
[0007] As also illustrated in FIG. 1, an interfering or jamming
signal z(t) having a corresponding frequency domain representation
Z(f) is coupled to output port 105, for example from a device such
an antenna that is connected to output port 105. In general, Z(f)
may include substantial components at several different frequencies
and/or over a range of frequencies, but for simplification of
explanation, it will be assumed for the remainder of this
discussion that that J(f) is essentially a single frequency signal
at a second frequency F2.
[0008] The present inventors have appreciated that for at least
some passive devices, output port 105 may act as a mixing node
whereby the first frequency F1 of the input signal is mixed with
the second frequency F2 of the interfering or jamming signal. In
that case, the signal Y(f) may have frequency components Fi
according to equation (1):
Fi=.+-.aF1.+-.bF2, where a and b are integers, and where
a.epsilon.(0,.infin.), and b.epsilon.(0,.infin.) (1)
[0009] In the cases where a.noteq.0 and b.noteq.0, the resultant
frequency component Fi is an intermodulation product, as described
above.
[0010] In many systems and applications, certain intermodulation
products are of greater concern than others. Often, the most
important intermodulation products are the 3.sup.rd (third) order
intermodulation products where a=2 and b=1, and where a=1 and b=2,
namely:
F3(Lo)=2F1F2; and (2)
F3(Hi)=2F2F1, (3)
where here it is assumed that F2>F1.
[0011] For example, when F2=1 GHz and F1=900 MHz, then F3(Lo)=800
MHz, and F3(Hi)=1.1 GHz. As can be seen, these third order
intermodulation products have frequencies which fall relatively
close to the frequency F1 of the original input signal, and
therefore may be difficult to separate from the input signal by
filtering, and may be received by receivers that are intended to
receive the input signal, etc. Other "odd order" intermodulation
products such as 5.sup.th (fifth) order (e.g., 3F2-2F1 and
3F1-2F2), 7.sup.th (seventh) order (e.g., 4F2-3F1 and 4F1-3F2),
etc. and higher order intermodulation products may also include
frequencies that are relatively close to the original frequency of
the input signal, however the magnitude of these products is
typically substantially less than the magnitudes of the third order
IM products.
[0012] FIG. 2 depicts an example for illustrating intermodulation
products being generated by a mixing operation of a passive
three-port device, namely a duplexer 200.
[0013] As illustrated in FIG. 2, duplexer 200 receives at a
transmit input port 201 a transmit signal x.sub.T(t) having a
corresponding frequency domain representation X.sub.T(f) which
passes through a transmit filter of duplexer 200 and is provided to
a common port 205 thereof. In many systems, common port 205 may be
connected to an antenna, and so common port 205 is often also
referred to as an antenna port. Meanwhile, duplexer 200 receives at
common port 205 a signal z.sub.R(t) having a corresponding
frequency domain representation Z.sub.R(f) which passes through a
receive filter of duplexer 200 and is provided to a receive port
203 thereof as a receive signal x.sub.R(t)/X.sub.R(f).
[0014] In general, both X.sub.T(f) and X.sub.R(f) may include
substantial components at several different frequencies and/or over
a range of frequencies, but for simplification of explanation, it
will be assumed for the remainder of this discussion that the
portions of X.sub.T(f) and X.sub.R(f) that are of interest are each
essentially single frequency signals at first and second
frequencies F1 and F2, respectively.
[0015] As also illustrated in FIG. 2, an interfering or jamming
signal j(t) having a corresponding frequency domain representation
J(f) may also be coupled to common port 205, for example from an
antenna that is connected to common port 205. In general, J(f) may
include substantial components at several different frequencies
and/or over a range of frequencies, but for simplification of
explanation, it will be assumed for the remainder of this
discussion that that the portions J(f) that is of interest is
essentially a single frequency signal at a third frequency F3.
[0016] The present inventors have appreciated that for at least
some three-port devices, common port 205 may act as a mixing node
whereby the first frequency F1 of the transmit signal is mixed with
the third frequency F3 of the interfering or jamming signal. There
may also be "internal" mixing nodes which are internal to duplexer
200 and whose mixing products could pass through to common port
105. In that case, X.sub.R(f)) appearing at receive port 203 may
include intermodulation products of F1 and F3, i.e.,
.+-.aF1.+-.bF3, where a and b are integers, and where a.epsilon.(0,
.infin.), and b.epsilon.(0, .infin.).
[0017] Some of the frequency components comprising these
intermodulation products may fall within the reception band--a band
which is being received by the receiver circuitry that may be
connected to receive port 203. In that case, these intermodulation
products become interfering signals for reception of the desired
signal x.sub.R(t)/X.sub.R(f)). To address this problem, some
existing apparatuses may try to use filtering to eliminate or
reduce the magnitude of the jamming signal. For example a notch
filter may be placed at the ANT port of such a duplexer to pass the
transmit and receive signals while notching out (blocking) the
jammer signal. However, when the jamming signal is located close in
frequency to the desired signal(s) to be processed, the required
notch filter--in order to reject the undesired jammer--will
typically have a high insertion loss, which is undesirable, and in
some cases will also give rise to its own 3.sup.rd order IM
generation. Another complicating factor is that the notch filter
may need to be tunable to be able to reject the undesired jammer
while passing the desired transmit and receive signals. Such a
notch filter would need to be simultaneously tunable, linear, and
highly frequency selective.
[0018] What is needed, therefore, is an arrangement for reducing,
removing, or eliminating one or more intermodulation products that
may be generated by a mixing operation of a passive device without
the use of a high insertion loss filter.
SUMMARY
[0019] In one aspect of the invention, an apparatus comprises: a
first apparatus port configured to receive a first signal having a
first frequency; a second apparatus port configured to output the
first signal having the first frequency; a first passive device
connected between the first and second apparatus ports; a second
passive device connected between the first and second apparatus
ports; a plurality of phase shifters each configured to provide a
corresponding phase shift, wherein at least one of the phase
shifters is configured to provide its corresponding phase shift in
a first signal path between the first and second apparatus ports
through the first passive device, and wherein at least another of
the phase shifters is configured to provide its corresponding phase
shift in a second signal path between the first and second
apparatus ports through the second passive device, wherein the
phase shifts are selected to cancel one of an upper or lower
intermodulation product between the first signal, and a second
signal having a second frequency received at the second apparatus
port.
[0020] In one or more embodiments, the phase shifts may be selected
to cancel one of an upper or lower third order intermodulation
product between the first signal and the second signal.
[0021] In one or more embodiments, the phase shifts may be selected
to cancel one of an upper or lower Nth order intermodulation
product between the first signal and the second signal, where N is
an odd number greater than 3.
[0022] In one or more embodiments, the first and second passive
devices each may have a corresponding first device port and a
corresponding second device port, and wherein the plurality of
phase shifters are configured to provide: a first phase shift
between the first apparatus port and the first device port of the
first passive device; and a second phase shift between the second
apparatus port and the second device port of the second passive
device.
[0023] According to one optional feature of these embodiments, the
first and second phase shifts may each be approximately +90 degrees
or -90 degrees at the first frequency.
[0024] According to one optional feature of these embodiments, the
first and second phase shifts may each be approximately +45 degrees
or -45 degrees at the first frequency.
[0025] In one or more embodiments, the first and second passive
devices may each have a corresponding first device port and a
corresponding second device port, and wherein the plurality of
phase shifters are configured to provide: a negative phase shift of
a defined phase angle at the first frequency between the first port
of the apparatus and the first device port of the first passive
device; a positive phase shift of the defined phase angle at the
first frequency between the first port of the apparatus and the
first device port of the second passive device; a positive phase
shift of the defined phase angle at the first frequency between the
second port of the apparatus and the second port of the first
passive device; and a negative phase shift of the defined phase
angle at the first frequency between the second port of the
apparatus and the second port of the second passive device.
[0026] According to one optional feature of these embodiments, the
defined phase angle may be approximately 45 degrees.
[0027] According to one optional feature of these embodiments, the
defined phase angle may be approximately 22.5 degrees.
[0028] In one or more embodiments, each of the first and second
passive devices is a filter.
[0029] In one or more embodiments, the first and second passive
devices may have approximately the same S-parameters as each
other.
[0030] According to one optional feature of these embodiments, the
apparatus may have S-parameters which are approximately the same as
the S-parameters of the first and second passive devices.
[0031] In one or more embodiments, the first passive device and the
second passive device may be configured to apply a same phase shift
as each other at the first frequency.
[0032] In one or more embodiments, the apparatus may further
comprise a transmit amplifier coupled to the first port of the
apparatus and configured to provide the first signal to the first
port of the apparatus.
[0033] According to one optional feature of these embodiments, the
apparatus may further comprise an antenna coupled to the second
port of the apparatus and configured to receive the first signal
from the second port of the apparatus.
[0034] In one or more embodiments, the apparatus may further
comprise at least one circulator connected between at least one of
the phase shifters and at least one of the first and second
apparatus ports.
[0035] In one or more embodiments, the apparatus may further
comprise at least one power splitter/combiner connected between at
least one of the phase shifters and at least one of the first and
second apparatus ports, wherein the splitter/combiner is configured
to split a single signal path into two signals paths such that in a
reverse direction a differential mode is absorbed.
[0036] In another aspect of the invention, an apparatus comprises:
a first apparatus port configured to receive a first signal having
a first frequency; a second apparatus port; a third apparatus port
configured to output the first signal having the first frequency
and to receive a second signal having a second frequency, wherein
the second apparatus port is configured to output the second signal
having the second frequency; first, second, third, and fourth
passive devices, each having a corresponding first device port and
a corresponding second device port, wherein the second device ports
of the first and third passive devices are connected together with
a first impedance matching device and the second device ports of
the second and fourth passive devices are connected together with a
second impedance matching device, a plurality of phase shifters
each configured to provide a corresponding phase shift, wherein at
least one of the phase shifters is configured to provide its
corresponding phase shift in a first signal path between the first
and third apparatus ports through the first passive device, wherein
at least another of the phase shifters is configured to provide its
corresponding phase shift in a second signal path between the first
and third apparatus ports through the second passive device,
wherein still another of the phase shifters is configured to
provide its corresponding phase shift in a third signal path
between the second and third apparatus ports through the third
passive device, and wherein yet another of the phase shifters is
configured to provide its corresponding phase shift in a fourth
signal path between the second and third apparatus ports through
the fourth passive device; wherein the phase shifts are selected to
cancel one of an upper or lower intermodulation product between the
first signal, and a third signal having a third frequency received
at the third apparatus port In one or more embodiments, the phase
shifts may be selected to cancel one of an upper or lower third
order intermodulation product between the first signal and the
second signal.
[0037] In one or more embodiments, the phase shifts may be selected
to cancel one of an upper or lower Nth order intermodulation
product between the first signal and the second signal, where N is
an odd number greater than 3.
[0038] In one or more embodiments, the first, second, third and
fourth passive devices may each have a corresponding first device
port and a corresponding second device port, and wherein the
plurality of phase shifters are configured to provide: a first
phase shift between the first apparatus port and the first device
port of first passive device; a second phase shift between the
second apparatus port and the first device port of third passive
device; and a third phase shift between the second impedance
matching element and third apparatus port, wherein the first phase
shift, second phase shift, and third phase shift are all
approximately equal to each other.
[0039] In one optional feature of these embodiments, the first,
second and third phase shifts may each be approximately +90 degrees
or -90 degrees the first frequency.
[0040] In one optional feature of these embodiments, the first,
second and third phase shifts may each be approximately +45 degrees
or -45 degrees at the first frequency.
[0041] In one or more embodiments, the first, second, third, and
fourth passive devices each have a corresponding first device port
and a corresponding second device port, and wherein the plurality
of phase shifters are configured to provide: a positive phase shift
of a defined phase angle at the first frequency between the first
apparatus port and the first device port of first passive device; a
negative phase shift of the defined phase angle at the first
frequency between the first apparatus port and the first device
port of second passive device; a positive phase shift of the
defined phase angle at the first frequency between the second
apparatus port and the first device port of third passive device; a
negative phase shift of the defined phase angle at the first
frequency between the second apparatus port and the first device
port of fourth passive device; a negative phase shift of the
defined phase angle at the first frequency between the first
impedance matching device and the third apparatus port; and a
positive phase shift of the defined phase angle at the first
frequency between the second impedance matching device and the
third apparatus port.
[0042] In one optional feature of these embodiments, the defined
phase angle may be approximately 45 degrees.
[0043] In one optional feature of these embodiments, the defined
phase angle may be approximately 22.5 degrees.
[0044] In one or more embodiments, the apparatus may further
comprise at least one circulator connected between at least one of
the phase shifters and at least one of the first, second and third
apparatus ports.
[0045] In one or more embodiments, the apparatus may further
comprise at least one power splitter/combiner connected between at
least one of the phase shifters and at least one of the first,
second and third apparatus ports, wherein the splitter/combiner is
configured to split a single signal path into two signals paths
such that in a reverse direction a differential mode is
absorbed.
[0046] In one or more embodiments, the first and second passive
devices may be transmit filters, and the third and fourth passive
devices may be receive filters.
[0047] In one or more embodiments, the apparatus may be a filter, a
duplexer, or a quadraplexer with differential receive ports.
[0048] In one or more embodiments, the apparatus may further
comprise: a fourth apparatus port; and fifth and sixth passive
devices each having a corresponding first device port and a
corresponding second device port, wherein the second device port of
the fifth passive device is connected to the first impedance
matching device, and wherein the second device port of the sixth
passive device is connected to the second impedance matching
device.
[0049] In one optional feature of these embodiments, the apparatus
may further comprise: a first pull down device connected to first
impedance matching device, and a second pull down device connected
to second impedance matching device, wherein the first and second
pull down devices reduce a voltage of the third signal at the third
frequency at the second device ports of the first and second
devices.
[0050] In one optional feature of these embodiments, the plurality
of phase shifters may be configured to provide: a first phase shift
between the first apparatus port and the first device port of first
passive device; a second phase shift between the second apparatus
port and the first device port of third passive device; a third
phase shift between the second impedance matching element and third
apparatus port; and a fourth phase shift between fourth apparatus
port and the first device port of the fifth passive device, wherein
the first phase shift, second phase shift, third phase shift, and
fourth phase shift are all approximately equal to each other.
[0051] In one optional feature of these embodiments, the first,
second and third phase shifts may each be approximately +90 degrees
or -90 degrees at the first frequency.
[0052] In one optional feature of these embodiments, the first,
second, and third phase shifts may each be approximately +45
degrees or -45 degrees at the first frequency.
[0053] In one optional feature of these embodiments, the apparatus
may further comprise at least one circulator connected between at
least one of the phase shifters and at least one of the first,
second, third and fourth apparatus ports.
[0054] In one optional feature of these embodiments, the apparatus
may further comprise at least one power splitter/combiner connected
between at least one of the phase shifters and at least one of the
first, second, third and fourth apparatus ports, wherein the
splitter/combiner is configured to split a single signal path into
two signals paths such that in a reverse direction a differential
mode is absorbed.
[0055] In one optional feature of these embodiments, the plurality
of phase shifters may be configured to provide: a positive phase
shift of the defined phase angle at the first frequency between the
first apparatus port and the first device port of first passive
device; a negative phase shift of the defined phase angle at the
first frequency between the first apparatus port and the first
device port of second passive device; a positive phase shift of the
defined phase angle at the first frequency between the second
apparatus port and the first device port of third passive device; a
negative phase shift of the defined phase angle at the first
frequency between the second apparatus port and the first device
port of fourth passive device; a negative phase shift of the
defined phase angle at the first frequency between the first
impedance matching device and the third apparatus port; a positive
phase shift of the defined phase angle at the first frequency
between the second impedance matching device and the third
apparatus port; a positive phase shift of the defined phase angle
at the first frequency between the fourth apparatus port and the
first device port of fifth passive device; a negative phase shift
of the defined phase angle at the first frequency between the
fourth apparatus port and the first device port of sixth passive
device.
[0056] In one optional feature of these embodiments, the defined
phase angle may be approximately 45 degrees.
[0057] In one optional feature of these embodiments, the defined
phase angle may be approximately 22.5 degrees.
[0058] In one optional feature of these embodiments, the first and
second passive devices may be transmit filters, the third and
fourth passive devices may be receive filters, and the fifth and
sixth passive devices may be receive filters operating in a
different frequency band from first through fourth filters.
[0059] In one optional feature of these embodiments, the first,
third and fifth passive devices may form a first quadraplexer, and
the second, fourth and sixth passive devices may form a second
quadraplexer.
[0060] In one optional feature of these embodiments, the first and
second quadraplexers may have approximately the same S-parameters
as each other.
[0061] In one optional feature of these embodiments, the apparatus
may have S-parameters which are approximately the same as the
S-parameters of the first and second quadraplexers.
[0062] In one optional feature of these embodiments, the first and
third passive devices may form a first duplexer, and the second and
fourth passive devices may form a second duplexer.
[0063] In one optional feature of these embodiments, the first and
second duplexers may have approximately the same S-parameters as
each other.
[0064] In one optional feature of these embodiments, the apparatus
may have S-parameters which are approximately the same as the
S-parameters of the first and second duplexers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] The example embodiments are best understood from the
following detailed description when read with the accompanying
drawing figures. It is emphasized that the various features are not
necessarily drawn to scale. In fact, the dimensions may be
arbitrarily increased or decreased for clarity of discussion.
Wherever applicable and practical, like reference numerals refer to
like elements.
[0066] FIG. 1 depicts an example for illustrating intermodulation
products being generated by a mixing operation of a passive
device.
[0067] FIG. 2 depicts an example for illustrating intermodulation
products being generated by a mixing operation of a duplexer
[0068] FIG. 3 illustrates a first example embodiment of an
apparatus having a double phase-matched configuration.
[0069] FIG. 4 illustrates a second example embodiment of an
apparatus having a double phase-matched configuration.
[0070] FIG. 5A illustrates a third example embodiment of an
apparatus having a double phase-matched configuration.
[0071] FIG. 5B illustrates a modification of the third example
embodiment of an apparatus having a double phase-matched
configuration.
[0072] FIG. 6 illustrates a fourth example embodiment of an
apparatus having a double phase-matched configuration.
[0073] FIG. 7 illustrates a fifth example embodiment of an
apparatus having a double phase-matched configuration.
[0074] FIG. 8 illustrates one embodiment of a Wilkinson device.
[0075] FIG. 9 illustrates a sixth example embodiment of an
apparatus having a double phase-matched configuration.
[0076] FIG. 10 illustrates a communication device that includes a
pair of apparatuses having a double phase-matched
configuration.
DETAILED DESCRIPTION
[0077] In the following detailed description, for purposes of
explanation and not limitation, example embodiments disclosing
specific details are set forth in order to provide a thorough
understanding of an embodiment according to the present teachings.
However, it will be apparent to one having ordinary skill in the
art having had the benefit of the present disclosure that other
embodiments according to the present teachings that depart from the
specific details disclosed herein remain within the scope of the
appended claims. Moreover, descriptions of well-known apparati and
methods may be omitted so as to not obscure the description of the
example embodiments. Such methods and apparati are clearly within
the scope of the present teachings.
[0078] As used herein, the term "radio frequency" or "RF" pertains
to VHF, UHF, SHF, microwave and even millimeter wave frequencies to
the extent that technology permits the devices and circuits
disclosed herein to be fabricated and operated at such frequencies.
Also, unless otherwise noted, when a first device is said to be
connected or coupled to a second device, this encompasses cases
where one or more intermediate devices may be employed to connect
the two devices to each other. In contrast, when a first device is
said to be directly connected or directly coupled to a second
device, this encompasses cases where the two devices are connected
together without any intervening devices except any necessary
electrical wires. As used herein, "approximately" means within
.+-.10%, and "substantially" means at least 90%.
[0079] FIG. 3 illustrates a first example embodiment of an
apparatus 300 having a double phase-matched configuration. In
various embodiments, apparatus 300 may be a filter, including for
example a notch filter.
[0080] Apparatus 300 includes: a first apparatus port (e.g., an
input port) 301 configured to receive a first (e.g., a transmit, or
TX) signal having a first frequency (F1); a second apparatus port
(e.g., an output port) 305 configured to output an output signal at
the first frequency F1; a first passive device 310 connected
between first and second apparatus ports 301 and 305; a second
passive device 320 connected between first and second apparatus
ports 301 and 305; and phase shifters 312, 314, 322 and 324.
[0081] Beneficially, first and second passive devices 310 and 320
each exclusively include passive components such as resistors,
capacitors, inductors, signal traces, crystals, acoustic wave
elements (including surface acoustic wave (SAW), bulk acoustic wave
(BAW), and film bulk acoustic wave (FBAR) devices, etc.
Beneficially, first and second passive devices 310 and 320 do not
include active components, such as amplifiers, transistors, etc. In
some embodiments, passive devices 310 and 320 may each comprise a
filter, for example a notch filter, or a resonator. Beneficially,
the phase responses of first and second passive devices 310 and 320
are closely matched such that the first (TX) signal experiences the
same, or nearly the same, phase shift when it passes through second
passive device 320 as it does when passing through first passive
device 310.
[0082] Phase shifters 312 and 322 are arranged in a first signal
path between first and second apparatus ports 301 and 305 through
first passive device 310, and phase shifters 314 and 324 are
arranged in a second signal path between first and second apparatus
ports 301 and 305 through second passive device 320. First passive
devices 310 and 320 each have a first device port (e.g., an input
port) 311 and 321, respectively, and a second device port (e.g., an
output port) 315 and 325 respectively. That is: phase shifter 312
is connected between first apparatus port 301 and first device port
311; phase shifter 314 is connected between first apparatus port
301 and first device port 321; phase shifter 322 is connected
between second apparatus port 305 and second device port 315; and
phase shifter 324 is connected between second apparatus port 305
and second device port 325.
[0083] Phase shifters 312 and 324 are each configured to provide a
negative phase shift -.theta., and phase shifters 314 and 322 are
each configured to provide a positive phase shift +.theta.. Phase
shifters 312, 314, 322 and 324 may employ any convenient technology
to realize the desired phase shift, including without limitation, a
transmission line, a switched line (delay line) phase shifter, a
switched filter phase shifter, a high-pass/low-pass phase shifter,
a loaded line phase shifter, a ferroelectric phase shifter, a
varactor phase shifter, a Schiffman phase shifter, a Hilbert
transform device, etc.
[0084] Beneficially, each of the phase shifters 312, 314, 322 and
324 has a low or minimal loss, and it is particularly beneficial if
the losses through the phase shifters 312 and 314 closely match
each other, and the losses through the phase shifters 322 and 324
also closely match each other.
[0085] It should be understood that each of the phase shifters 312,
314, 322 and 324 could be realized with a concatenation of
individual phase shifting elements each having their own phase
shift amounts that when added together produce the total phase
shift of -.theta. for phase shifters 312 and 324 and +.theta. for
phase shifters 314 and 322.
[0086] In some embodiments, first and second passive devices 310
and 320 have the same, or approximately the same, S-parameters as
each other. In some embodiments, apparatus 300 has S-parameters
which are the same, or approximately the same, as the S-parameters
of first and second passive devices 310 and 320.
[0087] In operation, a transmit signal TX having the first
frequency F1 is provided to first apparatus port 301, for example
from a transmit amplifier not shown in FIG. 3. A portion (e.g.,
50%) of the transmit signal TX is provided to each of the first
device ports 311 and 321 of first and second passive devices 310
and 320 via phase shifters 312 and 314, respectively. First and
second passive devices 310 and 320 each output a portion (e.g.,
50%) of the transmit signal TX, with some amplitude response (e.g.,
loss) and phase response applied thereto by the passive devices.
Beneficially, first and second passive devices 310 and 320 provide
the same, or approximately the same, amplitude response and phase
response as each other. First and second passive devices 310 and
320 may perform some operation with respect to the transmit signal
TX, for example filtering the transmit signal TX. The portions
(e.g., 50%) of the transmit signal TX output by each of first and
second passive devices 310 and 320 are combined and output at
second apparatus port (output port) 305. It is noted that,
beneficially, with the arrangement of phase shifters in apparatus
300, the phase shift of the transmit signal TX through a first
signal path including first passive device 310 and phase shifters
312 and 322 is equal or approximately equal to the phase shift of
the transmit signal TX through a second signal path including
second passive device 320 and phase shifters 314 and 324 such that
the transmit signal TX is left intact at second apparatus port
(output port) 305.
[0088] As illustrated in FIG. 3, an interfering or jamming signal J
having a second frequency F2 is coupled to second apparatus port
305 of apparatus 300, for example from a device such an antenna
that is connected to second apparatus port 305. In various
embodiments, the first frequency F1 of the transmit signal TX and
the second frequency F2 of the jamming signal J are each RF or
microwave frequencies. In some embodiments, F1 and F2 may be
frequencies employed for mobile communication devices, for example
mobile telephony devices, such as frequencies employed in various
countries for GSM, CDMA, LTE and similar communication systems.
[0089] In apparatus 300, a mixing operation between the transmit
signal TX at the first frequency F1 and the jamming signal J at the
second frequency F2 occurs at each of the second device ports 315
and 325. Also, there may be "internal" mixing nodes, other than
device ports 315 and 325, which are internal to passive devices 310
and 320 and whose mixing products could pass through to second
apparatus port 305. As a result of the mixing operation(s),
intermodulation products are generated between the transmit signal
TX at the first frequency F1 and the jamming signal J at the second
frequency F2, as described above.
[0090] Furthermore, if, for example, passive devices 310 and 320
are band pass filters, then the jamming signal J having the second
frequency F2, and the intermodulation signals produced by each
filter, would in general have frequencies that could fall below,
above, or in the pass band of those filters. Meanwhile, the
transmit signal TX having the first frequency F1 would need to pass
through both band pass filters largely unattenuated in such an
application. Similarly, in a band reject or notch filter
application where passive devices 310 and 320 are each band reject
or notch filters, the transmit signal TX having the first frequency
F1 would need to pass largely unattenuated through each band reject
filter, while the jamming signal J having the second frequency F2
would typically reside at a frequency that would fall inside of the
reject band of the filter, and that the intermodulation signals
produced by each filter would reside at a frequency that could fall
above, below, or inside of the reject band.
[0091] Beneficially, the phase shifts +.theta. and -.theta. are
selected to eliminate, or substantially eliminate, at the second
apparatus port 305 an upper or lower intermodulation product
between the transmit signal TX at the first frequency F1, and the
jamming signal J at the second frequency F2. Here an upper
intermodulation product refers to an intermodulation product whose
frequency is greater than F1 (and also F2, for that matter), and a
lower intermodulation product refers to an intermodulation product
whose frequency is less than F1 (and also F2), as described above.
In particular, the frequencies F1 of the transmit signal TX and F2
of the jamming signal J produce 3.sup.rd order intermodulation
products at two different frequencies FA and FB, where FA=2F1-F2
and FB=2F2-F1. For example, where F1=1 GHz and F2=900 MHZ, then FA
would be 1.1 GHz and FB would be 800 MHz. In this example, FA would
be the upper 3.sup.rd order IM product, and FB would be the lower
3.sup.rd order IM product. On the other hand, if F2 was greater
than F1, for example, F1=1 GHz and F2=1.1 GHz, then FA would be 900
MHz and FB would be 1.2 GHz. In this second example, FA would be
the lower 3.sup.rd order IM product, and FB would be the upper
3.sup.rd order IM product.
[0092] In some embodiments, .theta. may be selected to be
approximately .lamda./8 (45.degree.) at least at the first
frequency F1 of the transmit signal TX and frequencies near the
first frequency F1, and/or at the second frequency F2 the jamming
signal J and frequencies near the second frequency F2, and/or at
the frequency of intermodulation product FA and frequencies near
FA. In that case, it will be shown that the third order IM product
at the frequency FA=2F1-F2 will be canceled at the second apparatus
port 305.
[0093] In particular, if it is assumed that the phase angle of the
transmit signal TX at the first frequency F1 is defined to be zero
degrees at the first apparatus port (e.g., input port) 301, and if
.theta.=45.degree., then the phase .phi..sub.T, of the transmit
signal TX at second device port 315 will be .phi..sub.D-45.degree.,
where .phi..sub.D is the phase shift which the transmit signal
experiences passing through first passive device 310. Meanwhile if
it is assumed that the phase angle of the jamming signal J at the
second frequency F2 is defined to be zero degrees at the second
apparatus port (e.g., output port) 305, then the phase .phi..sub.J
of the jamming signal at second device port 315 will be 45.degree..
So, the phase .phi..sub.IMD3 of the third order IM product at the
frequency FA which is generated at second device port 315 of first
passive device 310, will be:
.phi..sub.IMD3=2.phi..sub.T-.phi..sub.J=2(.phi..sub.D-45.degree.)-45.deg-
ree. (4)
[0094] When the third order IM product at the frequency FA
generated at second device port 315 passes through phase shifter
322, the resulting phase at second apparatus port 305 of the third
order IM product generated at second device port 315 is:
.phi..sub.IMD3=(2.phi..sub.T-.phi..sub.J=2(.phi.-45.degree.)-45.degree.)-
+45.degree. (5)
[0095] Meanwhile, the phase .phi..sub.IMD3 of the third order IM
product at the frequency FA which is generated at second device
port 325 of second passive device 320, will be:
.phi..sub.IMD3=2.phi..sub.T-.phi..sub.J=2(.phi..sub.D+45.degree.)+45.deg-
ree. (6)
[0096] When the third order IM product at the frequency FA
generated at second device port 325 passes through phase shifter
324, the resulting phase at second apparatus port 305 of the third
order IM product generated at second device port 325 is:
.phi..sub.IMD3=(2.phi..sub.T-.phi..sub.J=2(.phi..sub.D+45.degree.)+45.de-
gree.)-45.degree. (7)
[0097] From equations (5) and (7), it can be seen that at second
apparatus port 305, the phase difference .DELTA..phi. between the
third order IM product at the frequency FA generated at second
device port 315, and the third order IM product at the frequency FA
generated at second device port 325, is:
.DELTA. .phi. = [ 2 ( .phi. D - 45 .degree. ) - 45 .degree. ) + 45
.degree. ] - [ ( 2 ( .phi. D + 45 .degree. ) + 45 .degree. ) - 45
.degree. ] = [ 2 ( .phi. D - 45 .degree. ) ] - [ 2 ( .phi. D + 45
.degree. ) ] = - 180 .degree. ( 8 ) ##EQU00001##
[0098] From equation (8) it can be seen that when
.theta.=45.degree., then the third order IM product at the
frequency FA generated at second device port 315, and the third
order IM product at the frequency FA generated at second device
port 325, are 180 degrees out of phase at second apparatus port
305.
[0099] Therefore, if the amplitudes of the third order IM product
at the frequency FA generated at second device port 315 and the
third order IM product at the frequency FA generated at second
device port 325, are the same or approximately the same as each
other, and any signal loss through phase shifters 322 and 324 are
approximately the same as each other, then these two third order IM
components will cancel, or substantially cancel each other out at
second apparatus port 305. This condition can be satisfied if, for
example, any loss through phase shifters 312 and 314 are
approximately the same as each other, any loss through first and
second passive devices 310 and 320 are approximately the same as
each other, and any loss through phase shifters 322 and 324 are
approximately the same as each other.
[0100] As long as the following two conditions are satisfied with
respect to the matched or nearly matched devices 310 and 320, the
intermodulation products generated by second device ports 315 and
325 and any "internal" mixing nodes of devices 310 and 320, along
with phase shifters 312, 314, 322 and 324 with an appropriately
selected phase shifts +.theta./-.theta., will be sufficient as to
give rise to the cancellation, or near cancellation, of an upper
(or lower) intermodulation product at output 305. (1) The internal
circuitry between every pair of nodes inside of each passive device
is identical or near identical in its electrical behavior--that is
the impedance (at the frequency F1 of the transmit signal TX, at
the frequency F2 of the jamming signal J, and at the
intermodulation frequencies FA and FB) is identical between any
such pair or nodes in each passive device 310 and 320. As such the
power of the transmit signal TX and the jamming signal J that flows
to and from every node will be identical in the passive devices 310
and 320. (2) The power which is produced at the intermodulation
signal frequencies FA and FB by any circuit element between any
pair of nodes within each passive device 310 and 320 is identical
or near identical.
[0101] An apparatus such as apparatus 300 where phase shifters
having appropriate phase shifts are employed to cancel out an upper
or lower intermodulation product at one of the apparatus ports is
referred to here as having a double phase-matched configuration.
This should be distinguished from a double balanced configuration,
such as is employed in a double balanced mixer. For example, in
general a double balanced mixer is a three-port device which
receives an RF signal at a first port, and a local oscillator (LO)
signal at a second port, and which outputs at a third port a mixed
signal which is the product of the RF signal and the LO signal. The
double balanced mixer suppresses the power of both the RF signal
and the LO signal appearing at the third port, while passing the
mixed tones, including the upper and lower intermodulation
products, to the third port. In a double balanced mixer, the word
"double" refers to the fact that the device includes two baluns
which are used to suppress the amount of the RF signal and the LO
signal that appear at the third port. In direct contrast to this,
in the apparatus 300, for example, it is desired to pass the power
of the transmit signal TX to the second apparatus port 305, while
suppressing at apparatus port 305 the power of an intermodulation
mixing product between the transmit signal TX and the jamming
signal J.
[0102] From the above discussion, it is seen that by an appropriate
selection of .theta., the magnitude of the third order IM product
at frequency FA appearing at second apparatus port 305 of apparatus
300 having the double phase-matched configuration may be
substantially reduced when compared with the magnitude of the third
order IM product at frequency FA appearing at the second device
port 315 or 325 of any one individual passive device 310 or 320.
For example, in some embodiments the ratio between: (1) the
magnitude of the transmit signal TX at frequency F1 appearing at
second apparatus port 305, and (2) the magnitude of the third order
IM product at frequency FA appearing at second apparatus port 305
may be 20 dB or more compared to the ratio between: (1) the
magnitude of the transmit signal TX at frequency F1 appearing at
second device port 315 or 325, and (2) the magnitude of the third
order IM product at frequency FA appearing at second device port
315 or 325.
[0103] It should be noted that some of the reduction in the
magnitude of the IM products occurs simply due to the splitting of
power between the two passive devices 310 and 320. That is, if the
devices are not in saturation with respect to the IM products, so
that weak nonlinear power dependence applies, the power density of
the transmit signal TX and the jamming signal J are each reduced by
a factor of two due to splitting transmit signal TX and the jamming
signal J into two paths entering two devices, and hence the net
magnitude of the IM product produced by the mixers in each device
will likely fall by 9 dB relative to a single device. In other
words, if the phase shift A was set to zero, then the power of the
IM products from two passive devices 310 and 320 in parallel with
each other would be -6 dB (i.e., -9 dB less per device, multiplied
by 2 devices (+3 db)=-6 dB) with respect to the case where a single
device were employed. As explained above, by the appropriate choice
of phase A the (lower or upper) IM product can be suppressed much
more than by 6 dB. It should also be noted that the cancelation or
substantial cancellation of the (lower or upper) IM product using
the double phase-matched configuration described above does not
require that the device IM products are not in saturation, so that
weak nonlinear power dependence applies. As long as the two passive
devices 310 and 320 have internal mixers that generate the same
level of IM power independent of the power of the transmit signal
TX and the jamming signal J, the cancellation will occur if the
appropriate phase angle .theta. is employed. That is, so long as
each device 310 and 320 has the same or near the same IM power
dependence as a function of the power of the transmit signal TX and
the jamming signal J, the cancellation will occur.
[0104] The inventors have also discovered that in some embodiments
the 3.sup.rd order IM cancellation described above may be provided
to a large degree even when .theta. is not precisely .lamda./8
(45.degree.). Indeed, in some embodiments 10 dB reduction of the
3.sup.rd order IM product at frequency FA has been observed over a
range of .+-.15% with respect to the "ideal" value of .theta. of
.lamda./8 (45.degree.).
[0105] In some embodiments, .theta. may be selected to be
approximately .lamda./16 (22.5.degree.) at least at the first
frequency F1 of the transmit signal TX and frequencies near the
first frequency F1, and/or at the second frequency F2 the jamming
signal J and frequencies near the second frequency F2, and/or at
the frequency of intermodulation product FB and frequencies near
FB. In that case, it can be shown using a similar analysis to that
performed above, and under similar conditions, that the third order
IM product at the frequency FB=2F2-F1 will be canceled, or
substantially canceled, at the second apparatus port 305, where
again F2 is again a frequency of the jamming signal J. For example,
in some embodiments the ratio between: (1) the magnitude of the
transmit signal TX at frequency F1 appearing at second apparatus
port 305, and (2) the magnitude of the third order IM product at
frequency FB appearing at second apparatus port 305 may be improved
by 20 dB or more compared to the ratio between: (1) the magnitude
of the transmit signal TX at frequency F1 appearing at second
device port 315 or 325, and (2) the magnitude of the third order IM
product at frequency FB appearing at second device port 315 or
325.
[0106] In other embodiments, other values of .theta. may be
selected to cancel, or substantially cancel, an upper or lower
5.sup.th order IM product, an upper or lower 7.sup.th order IM
product, etc.
[0107] Those skilled in the art will appreciate that when apparatus
300 having the double phase-matched configuration is substituted in
a larger system in place of a single passive device such as passive
device 310 or 320, appropriate measures must be taken to insure
that proper impedance matching is maintained. For example, if
passive device 310 was employed in a system where an amplifier
having a 50.OMEGA. output impedance was employed to supply the
first signal to the input of a single passive 310, then passive
device 310 should have a 50.OMEGA. input impedance at first device
port 311. In that case, the input impedance of apparatus 300 at
first apparatus port 301 would be 50.OMEGA.|50.OMEGA.=25.OMEGA.. To
address this issue, some embodiments may employ an impedance
matching transformer between the amplifier and first apparatus port
301. Other embodiments may employ modified passive devices 310 and
320 whose impedance has been doubled to 100.OMEGA.. A similar
discussion applies to the output impedance of passive device 310
and second apparatus port 305.
[0108] The present inventors have appreciated that the embodiment
illustrated in FIG. 3 can be modified so as to reduce the total
number of phase shifters by half. In particular, if the phase shift
of each of the phase shifters of FIG. 3 is either increased by
.theta. or decreased by .theta., the resultant apparatus may
operate substantially similarly to apparatus 300 with respect to
the elimination of an intermodulation product at the output port of
the apparatus, as described above.
[0109] Accordingly, FIG. 4 illustrates a second example embodiment
of an apparatus 400 having a double phase-matched configuration.
Apparatus 400 is similar to apparatus 300 shown in FIG. 3, and like
elements in FIG. 4 have like reference numerals, and for brevity a
description of the portions of apparatus 400 that are the same as
apparatus 300 will not be repeated.
[0110] As shown in FIG. 4, apparatus 400 has two phase shifters 412
and 424 in contrast to the four phase shifters employed in
apparatus 300. Phase shifter 412 has a phase shift of -2.theta. and
phase shifter 424 has a phase shift of +2.theta.. It will be
understood that apparatus 400 may be obtained from apparatus 300 by
subtracting .theta. from the phase shifts of each of the phase
shifters in apparatus 300. As a result, two of the phase shifters
have a phase shift of zero, and may be eliminated, and .theta. may
be selected, as with apparatus 300, for elimination of an
intermodulation product. For example, it can be shown using an
analysis similar to that performed above with respect to apparatus
300, that when .theta. is selected to be 45.degree. in apparatus
400 (i.e., 2.theta.=90.degree.), then the third order
intermodulation product at FA (2F1-F2) appearing at second
apparatus port 405 is eliminated, or substantially eliminated, by
cancelation of the products produced at the mixing nodes 315 and
325, where again F1 is the frequency of the transmit signal TX and
F2 is the frequency of the jamming signal J.
[0111] In practice, in some implementations there may be a small
penalty to be paid for the elimination of the two phase shifters in
apparatus 400 compared to apparatus 300. For example, in general
the phase shifters 412 and 424 may provide some small amplitude
loss that is not canceled out as in the apparatus 300. If phase
shifter 412 has a small loss at the first (transmit) frequency F1,
then the amplitudes of the transmit signal TX at the mixing nodes
315 and 325 may be slightly mismatched, thereby degrading the
degree of cancelation of the third order IM products at second
apparatus port 405. Similarly, if phase shifter 424 has a small
loss at the jamming frequency F2, then the amplitudes of the
jamming signal J at the mixing nodes 315 and 325 may be slightly
mismatched, again degrading the degree of cancelation of the third
order IM products at second apparatus port 405.
[0112] As with apparatus 300, it is noted that, beneficially, with
the arrangement of phase shifters in apparatus 400, the phase shift
of the transmit signal TX through a first signal path including
first passive device 310 and phase shifter 412 is equal or
approximately equal to the phase shift of the transmit signal TX
through a second signal path including second passive device 320
and phase shifter 424 such that the transmit signal TX is left
intact at second apparatus port 405.
[0113] FIG. 4 illustrates an example embodiment produced by
subtracting .theta. from the phase shifts of each of the phase
shifters in apparatus 300, thereby eliminating a first pair of the
four phase shifters in apparatus 300 (i.e., phase shifters 314 and
322). However, it will be understood by those skilled in the art
that another embodiment could be produced by instead adding .theta.
to the phase shifts of each of the phase shifters in apparatus 300.
In that case, the other pair of phase shifters (312 and 324) would
be eliminated from apparatus 300 instead of the first pair of phase
shifters 314 and 322.
[0114] Although the apparatuses 300 and 400 split the transmit
signal TX between two passive devices 310 and 320, it should be
understood that in other embodiments the number of passive devices
among with the transmit signal TX is split may be greater than two,
with the appropriate phase shifts being applied to each signal path
through each of the passive devices.
[0115] FIG. 5A illustrates a third example embodiment of an
apparatus 500 having a double phase-matched configuration.
Apparatus 500 is a three-port apparatus and includes: a first
apparatus port 501, a second apparatus port 503, and a third
apparatus port 505; first, second, third, and fourth passive
devices 543, 544, 545 and 546; and first, second, third, fourth,
fifth and sixth phase shifters 512, 514, 522, 524, 532 and 534.
[0116] First apparatus port 501 is configured to receive a first
signal (e.g., a transmit signal TX) having a first frequency F1.
Second apparatus port 503 is configured to output a second signal
(e.g., a receive signal RX) having a second frequency F2. Third
apparatus port 505 is configured to output the first signal, after
processing by apparatus 500, having the first frequency F1 and to
receive a signal having the second frequency F2 which it processes
to produce the second (receive) signal RX.
[0117] Beneficially, first, second, third, and fourth passive
devices 543, 544, 545 and 546 each exclusively include passive
components such as resistors, capacitors, inductors, signal traces,
crystals, acoustic wave elements (including surface acoustic wave
(SAW), bulk acoustic wave (BAW), and film bulk acoustic wave (FBAR)
devices, etc. First, second, third, and fourth passive devices 543,
544, 545 and 546 do not include active components, such as
amplifiers, transistors, etc.
[0118] In the example embodiment illustrated in FIG. 5A, first,
second, third, and fourth passive devices 543, 544, 545 and 546
each comprise a filter. In particular, first and second passive
devices 543 and 544 each comprise a transmit filter for the
transmit signal TX, and third and fourth passive devices 545 and
546 each comprise a receive filter for the receive signal RX. In
some embodiments, the transmit filters and receive filters may each
include a resonator, such as a bulk acoustic wave (BAW) resonator
or film bulk acoustic resonator (FBAR).
[0119] First, second, third, and fourth passive devices 543, 544,
545 and 546 each have a corresponding first device port and a
corresponding second device port. The second device ports of first
and third passive devices 543 and 545 are connected together with a
first impedance matching device 590 to form a first duplexer 541,
and the second device ports of second and fourth passive devices
544 and 546 are connected together with a second impedance matching
device 590 to form a second duplexer 542. Together, first and
second duplexers 541 and 542 form a dual duplexer 510. Although
FIG. 5A shows impedance matching device 590 as an inductor
connected to ground, other embodiments may employ a different
impedance termination device, for example a transmission line
(e.g., a quarter wave line) connected between fourth device 545 and
a common node through which the second device ports of first and
third passive devices 543 and 545 are connected to phase shifter
532.
[0120] Beneficially, the phase responses of first and second
passive devices 543 and 544 are closely matched such that the first
(TX) signal experiences the same, or nearly the same, phase shift
when it passes through second passive device 544 as it does when
passing through first passive device 543. Toward that end, in an
optional feature of the example embodiment illustrated in FIG. 5A,
first and second passive devices 543 and 544 are fabricated on the
same die as each other, which may be referred to as a TX die.
Similarly, third and fourth passive devices 545 and 546 may also
fabricated on the same die as each other, which may be referred to
as a RX die, so as to closely match the characteristics of third
and fourth passive devices 545 and 546 to each other.
[0121] First, third, and sixth phase shifters 512, 522 and 534 are
each configured to provide a positive phase shift +.theta., and
second, fourth and fifth phase shifters 514, 524 and 532 are each
configured to provide a positive phase shift +.theta.. As with
apparatuses 300 and 400, in apparatus 500 first, second, third,
fourth, fifth and sixth phase shifters 512, 514, 522, 524, 532 and
534 each may employ any convenient technology to realize the
desired phase shift, including without limitation, a transmission
line, a switched line (delay line) phase shifter, a switched filter
phase shifter, a high-pass/low-pass phase shifter, a loaded line
phase shifter, a ferroelectric phase shifter, a varactor phase
shifter, a Schiffman phase shifter, a Hilbert transform device,
etc.
[0122] First, second, third, fourth, fifth and sixth phase shifters
512, 514, 522, 524, 532 and 534 are each configured to provide a
corresponding phase shift to a signal or signals that pass
therethrough. In particular, first and fifth phase shifters 512 and
532 are each configured to provide a corresponding phase shift in a
first signal path between first and third apparatus ports 501 and
505 through first passive device 543. Second and sixth phase
shifters 514 and 534 are each configured to provide a corresponding
phase shift in a second signal path between first and third
apparatus ports 501 and 505 through second passive device 544.
Third and fifth phase shifters 522 and 532 are each configured to
provide a corresponding phase shift in a third signal path between
second and third apparatus ports 503 and 505 through third passive
device 545. Fourth and sixth phase shifters 524 and 534 are each
configured to provide a corresponding phase shift in a fourth
signal path between second and third apparatus ports 503 and 505
through fourth passive device 546.
[0123] It should be understood that each of the phase shifters 512,
514, 522, 524, 532 and 534 could be realized with a concatenation
of individual phase shifting elements each having their own phase
shift amounts that when added together produce a new phase shift of
+.theta. for phase shifters 512, 522 and 534, and -.theta. for
phase shifters 514, 524 and 532.
[0124] In some embodiments, first and second duplexers 541 and 542
have the same, or approximately the same, S-parameters as each
other. In some embodiments, apparatus 500 has S-parameters which
are the same, or approximately the same, as the S-parameters of
each of first and second duplexers 541 and 542.
[0125] In operation, a first (transmit) signal TX having the first
frequency F1 is provided to first apparatus port 501, for example
from a transmit amplifier not shown in FIG. 5A. A portion (e.g.,
50%) of the transmit signal TX is provided to each of the first
device ports of first and second passive devices 543 and 544 via
phase shifters 512 and 514, respectively. First and second passive
devices 543 and 544 each output a portion (e.g., 50%) of the
transmit signal TX, with some amplitude response (e.g., loss) and
phase response applied thereto by the passive devices.
Beneficially, first and second passive devices 543 and 544 provide
the same, or approximately the same, amplitude response and phase
response as each other. First and second passive devices 543 and
544 may perform some operation with respect to the transmit signal
TX, for example filtering the transmit signal TX in the example
embodiment of FIG. 5A. The portions (e.g., 50%) of the transmit
signal TX output by each of first and second passive devices 543
and 544 are combined and output at third apparatus port 505. It is
noted that, beneficially, with the arrangement of phase shifters in
apparatus 500, the phase shift of the transmit signal TX through a
first signal path including first passive device 543 and phase
shifters 512 and 532 is equal or approximately equal to the phase
shift of the transmit signal TX through a second signal path
including second passive device 544 and phase shifters 514 and 534
such that the transmit signal TX is left intact at third apparatus
port 505.
[0126] Meanwhile, a second (receive) signal RX having a second
frequency F2 is output from apparatus 500 at second apparatus port
503 to a receiver not shown in FIG. 5A in response to a signal
received at third apparatus port 505 and processed by third and
fourth passive devices 545 and 546. Beneficially, third and fourth
passive devices 545 and 546 each process a portion (e.g., 50%) of
the signal received at third apparatus port 505, with provide the
same, or approximately the same, amplitude response and phase
response as each other. Third and fourth passive devices 545 and
546 may perform some operation to produce the receive signal RX,
for example filtering the signal provided from third apparatus port
505 in the example embodiment of FIG. 5A. The signals output by
each of third and fourth passive devices 545 and 546 are combined
and output at second apparatus port 503 as the receive signal RX.
It is noted that, beneficially, with the arrangement of phase
shifters in apparatus 500, the received signal through a third
signal path including third passive device 545 and phase shifters
522 and 532 is equal or approximately equal to the phase shift of
the received signal through a fourth signal path including fourth
passive device 546 and phase shifters 524 and 534 such that the
receive signal RX is left intact at second apparatus port 503.
[0127] As illustrated in FIG. 5A, an interfering or jamming signal
J having a third frequency F3 is coupled to third apparatus port
505 of apparatus 500, for example from a device such an antenna
that is connected to third apparatus port 505. In various
embodiments, the first frequency F1 of the transmit signal TX, the
second frequency F2 of the receive signal RX, and the third
frequency F3 of the jamming signal J are each RF or microwave
frequencies. In some embodiments, F1, F2 and F3 may be frequencies
employed for mobile communication devices, for example mobile
telephony devices, such as frequencies employed in various
countries for GSM, CDMA, LTE and similar communication systems.
[0128] A mixing operation between the transmit signal TX at the
frequency F1 and the jamming signal J at the frequency F3 occurs at
each of the second device ports of devices 543, 544, 545 and 546.
As a result of this mixing operation, intermodulation products are
generated between the transmit signal at the frequency F1 and the
jamming signal J at the frequency F3, and these intermodulation
products may appear at the second apparatus port 503 and thereby
interfere with reception of the receive signal RX by a receiver
connected to second apparatus port 503.
[0129] Beneficially, the phase shifts provided by first, second,
third, fourth, fifth and sixth phase shifters 512, 514, 522, 524,
532 and 534 may be selected to cancel at second apparatus port 503
one of an upper or lower intermodulation product produced by the
transmit signal TX having the frequency F1, and the jamming signal
J having the third frequency F3.
[0130] In some embodiments, .theta. may be selected to be
approximately .lamda./16 (22.5.degree.) at least at the first
frequency F1 of the transmit signal TX and frequencies near the
first frequency F1, and/or at the third frequency F3 the jamming
signal J and frequencies near the third frequency F3, and/or at the
frequency of intermodulation product FC and frequencies near FC. In
that case, it can be shown by an analysis similar to that performed
above with respect to apparatus 300 of FIG. 3 that a third order IM
product at the frequency FC=2F1-F3 generated at the second device
ports of first and third devices 543 and 545 will be 180 degrees
out of phase at the second apparatus port 503 with a third order IM
product at the frequency FC generated at the second device ports of
second and fourth devices 544 and 546.
[0131] Therefore, if the amplitudes of the third order IM product
at the frequency FC generated at the second device ports of first
and third devices 543 and 545, and the third order IM product at
the frequency FC generated at the second device ports of second and
fourth devices 544 and 546, are the same or approximately the same
as each other, and any signal loss through third and fourth passive
devices 545 and 546 are approximately the same as each other, then
these two third order IM components will cancel, or substantially
cancel, each other out. This condition can be satisfied if, for
example, any loss through phase shifters 512 and 514 are
approximately the same as each other, any loss through first and
second passive devices 543 and 544 are approximately the same as
each other, any loss through phase shifters 522 and 524 are
approximately the same as each other, and any loss through third
and fourth passive devices 545 and 546 are approximately the same
as each other.
[0132] In some embodiments, .theta. may be selected to be
approximately .lamda./8 (45.degree.) at the first frequency F1 of
the transmit signal TX and frequencies near the first frequency F1,
and/or at the third frequency F3 the jamming signal J and
frequencies near the third frequency F3, and/or at the frequency of
intermodulation product FD and frequencies near FD. In that case,
it can be shown that, under the same conditions discussed above,
the third order IM product at the frequency FD=2F3-F1 will be
canceled, or substantially canceled, at the second apparatus port
503.
[0133] The present inventors have appreciated that the embodiment
illustrated in FIG. 5A can be modified so as to reduce the total
number of phase shifters in half. In particular, if the phase
shifts of each of the phase shifters of FIG. 5A is either increased
by .theta. or decreased by .theta., the resultant apparatus may
operate substantially the same as apparatus 500 with respect to the
elimination of an intermodulation product at the second apparatus
port, as described above.
[0134] In some applications, it may be desired for the receive
signal RX to be provided via a differential receive port.
Accordingly, FIG. 5B illustrates an example embodiment of an
apparatus 580 where each of the third and fourth passive devices
585 and 586 has a differential device port. Each line of the
differential device ports has a corresponding phase shifter
connected to it, as shown in FIG. 5B. The outputs of these phase
shifter are then connected to a differential apparatus port 583, as
also shown in FIG. 5B.
[0135] Accordingly, FIG. 6 illustrates a fourth example embodiment
of an apparatus 600 having a double phase-matched configuration.
Apparatus 600 is similar to apparatus 500 shown in FIG. 5A, and
like elements in FIG. 6 have like reference numerals, and for
brevity a description of the portions of apparatus 600 that are the
same as apparatus 500 will not be repeated.
[0136] As shown in FIG. 6, apparatus 600 has three phase shifters
612, 622 and 634 in contrast to the six phase shifters employed in
apparatus 500. All of the phase shifters 612, 622 and 634 have a
phase shift of +2.theta.. It will be understood that apparatus 600
may be obtained from apparatus 500 by subtracting .theta. from the
phase shifts of each of the phase shifters in apparatus 500. As a
result, three of the phase shifters have a phase shift of zero, and
may be eliminated, and .theta. may be selected, as with apparatus
500, for elimination of an intermodulation product. For example, it
can be shown using an analysis similar to that performed above with
respect to apparatus 500, that when .theta. is selected to be
22.5.degree. in apparatus 600 (i.e., 2.theta.=45.degree.), then the
third order intermodulation product at FC (2F1-F3) appearing at
second apparatus port 605 may be eliminated or substantially
eliminated where, again, F1 is a frequency of the transmit signal
TX and F3 is a frequency of the jamming signal J. Similarly, when
.theta. is selected to be 45.degree. in apparatus 600 (i.e.,
2.theta.=90.degree.), then the third order intermodulation product
at FD (2F3-F1) appearing at second apparatus port 605 may be
eliminated or substantially eliminated where, again, F1 is a
frequency of the transmit signal TX and F3 is a frequency of the
jamming signal J. As with apparatus 400, it will be understood by
those skilled in the art that another embodiment could be produced
by instead adding .theta. to the phase shifts of each of the phase
shifters in apparatus 500.
[0137] As with apparatus 500, beneficially, with the arrangement of
phase shifters in apparatus 600, the phase shift of the transmit
signal TX through a first signal path including first passive
device 543 and phase shifter 612 is equal or approximately equal to
the phase shift of the transmit signal TX through a second signal
path including second passive device 544 and phase shifter 634 such
that the transmit signal TX is left intact at third apparatus port
605. Furthermore, it is noted that, beneficially, with the
arrangement of phase shifters in apparatus 600, the received signal
through a third signal path including third passive device 545 and
phase shifter 632 is equal or approximately equal to the phase
shift of the received signal through a fourth signal path including
fourth passive device 546 and phase shifter 634 such that the
receive signal RX is left intact at second apparatus port 503.
[0138] In some embodiments of apparatuses 500 and 600, propagation
mode conversion issues may arise if the there are not proper
impedance terminations within the apparatus for both common and
differential modes of propagation.
[0139] To address this issue, FIG. 7 illustrates a fifth example
embodiment of an apparatus 700 having a double phase-matched
configuration and a plurality of Wilkinson devices. Apparatus 700
is similar to apparatus 500 shown in FIG. 5A, and for
simplification of the illustration, reference numerals of those
elements in FIG. 7 that are the same as in FIG. 5A are not repeated
in FIG. 7, and only those elements that differ from apparatus 500
are labeled in FIG. 7. Also, for brevity a description of the
portions of apparatus 700 that are the same as apparatus 500 will
not be repeated.
[0140] A principle difference between apparatus 700 and apparatus
500 is that apparatus 700 includes Wilkinson devices 752, 754 and
756 at first, second, and third apparatus ports 701, 703, and 705,
respectively. A principal advantage of the inclusion of Wilkinson
devices 752, 754 and 756 in apparatus 700 is that they may provide
good impedance terminations for both common and differential
propagation modes.
[0141] FIG. 8 illustrates one example embodiment of a Wilkinson
device which may be employed in apparatus 700 where 50.OMEGA.
impedance matching is desired. Wilkinson devices are sometimes
referred to in the art as Wilkinson combiners or Wilkinson
splitters, depending upon their use in a particular apparatus, and
are well known in the art, and so a detailed description of their
operating theory and principles will not be provided here.
[0142] Although FIG. 7 shows an embodiment where Wilkinson devices
752, 754 and 756 are employed, here and throughout this
specification when a Wilkinson device is mentioned, in general any
type of splitter/combiner in which there is a splitting of a single
signal path into two signals paths and such that in the reverse
direction the differential mode is absorbed may be employed.
[0143] Also, although apparatus 700 includes three Wilkinson
devices 752, 754 and 756, other embodiments may only include one or
two Wilkinson devices for one or two of the apparatus ports.
Additionally, it should be noted that while apparatus 700 is an
embodiment similar to apparatus 500 which includes six phase
shifters, in other embodiments one or more Wilkinson devices may be
added at the apparatus port(s) of apparatus 600 which only includes
three phase shifters.
[0144] As with apparatus 500, appropriate selections of the phase
shift .theta. in apparatus 700 may allow an upper or lower
intermodulation product to be eliminated, or substantially
eliminated, at second apparatus port 703. For example, if the phase
shift .theta. is selected to be 22.5.degree. or 45.degree., an
upper or lower third order intermodulation product may be
eliminated, or substantially eliminated, at second apparatus port
703.
[0145] FIG. 9 illustrates a sixth example embodiment of an
apparatus 900 having a double phase-matched configuration.
Apparatus 900 is similar to apparatus 700 shown in FIG. 7, and only
those elements that differ from apparatus 700 are labeled in FIG.
9. Also, for brevity a description of the portions of apparatus 900
that are the same as apparatus 700 will not be repeated.
[0146] A principle difference between apparatus 900 and apparatus
700 is that apparatus 900 includes circulators instead of Wilkinson
devices 752 and 754 at first and second apparatus ports 901 and
903, respectively. In particular, apparatus 900 includes: a first
circulator 962 connected between first apparatus port 901 and first
phase shifter 512, which is in turn connected to the first device
port of first passive device 543; a second circulator 964 connected
between first apparatus port 901 and second phase shifter 514,
which is in turn connected to the first device port of second
passive device 544; a third circulator 966 connected between second
apparatus port 903 and third phase shifter 522, which is in turn
connected to the first device port of third passive device 545; and
a fourth circulator 968 connected between second apparatus port 903
and fourth phase shifter 524, which is in turn connected to the
first device port of fourth passive device 546. A principal benefit
of first, second, third and fourth circulators 962, 964, 966 and
968 in apparatus 900 is that they may provide good impedance
terminations for both common and differential propagation modes for
first and second duplexers 541 and 542.
[0147] Apparatus 900 includes: one Wilkinson device 756 connected
between the second device ports of first through fourth passive
devices 543/544/545/546 (i.e., the "common" or ANT ports of
duplexers 541/542) and third apparatus port 905; a pair of
circulators 962/964 connected between the first device ports of
first and second passive devices 543/544 (i.e., the TX ports of
duplexers 541/542) and first apparatus port 901; and another pair
of circulators 966/968 connected between the first device ports of
third and fourth passive devices 545/546 (i.e., the RX ports of
duplexers 541/542) and second apparatus port 904. However, other
embodiments may employ omit Wilkinson device 756 or one or more of
the pairs of circulators. Indeed various embodiments may employ any
desired combination of one or more Wilkinson devices as shown in
FIG. 7, and one or more pairs of circulators as shown in FIG. 9
between the various device ports and the apparatus ports.
Additionally, it should be noted that while apparatus 900 is an
embodiment similar to apparatus 500 which includes six phase
shifters, in other embodiments, circulators may be added at the
device port(s) of apparatus 600 which only includes three phase
shifters.
[0148] As with apparatus 500, appropriate selections of the phase
shift .theta. in apparatus 900 may allow an upper or lower
intermodulation product to be eliminated, or substantially
eliminated, at second apparatus port 903. For example, if the phase
shift .theta. is selected to be 22.5.degree. or 45.degree., an
upper or lower third order intermodulation product may be
eliminated, or substantially eliminated, at second apparatus port
903.
[0149] Although in general the principles described above for
apparatuses 500, 600, 700 and 900 can be applied to general to any
three port devices, the specific examples described above were
duplexers. The benefits of the double phase-matched configuration
of these apparatuses in terms of the elimination or substantial
reduction in an intermodulation product can be particularly
attractive in certain communication devices, particularly
communication devices that employ a wide range of frequencies,
including frequencies in different frequency bands. Examples of
such devices include mobile communication devices, in particular
multiband mobile telephones which may also include data
communication capabilities.
[0150] FIG. 10 illustrates a communication device 1000 that
includes a pair of apparatuses each having a double phase-matched
configuration. In particular, communication device 1000 is a
multi-band mobile telephone which employs frequency diversity and
operates in at least two frequency bands, here designated using the
frequency band designators B5 and B13 which are conventionally
understood in the art.
[0151] Communication device 1000 includes a first four-port
apparatus 1100 and a second four-port apparatus 1200. First
apparatus 1100 and second apparatus 1200 are each
quadraplexers.
[0152] First apparatus 1100 includes: a first apparatus port 1101
which receives a transmit signal in a first transmit frequency band
B5_TX; a second apparatus port 1103 which outputs a receive signal
in the first receive frequency band B5_RX; a third apparatus port
1105 which is connected to a first antenna 1005; and a fourth
apparatus port 1107 which outputs a diversity receive signal
(B13_D_RX) in a second receive frequency band B13_RX. Second
apparatus 1200 includes: a first apparatus port 1201 which receives
a transmit signal in a second transmit frequency band B13_TX; a
second apparatus port 1203 which outputs a receive signal in the
second receive frequency band B13_RX; a third apparatus port 1205
which is connected to a second antenna 1055; and a fourth apparatus
port 1207 which outputs a diversity receive signal (B5_D_RX) in the
first receive frequency band B5_RX.
[0153] First and second apparatuses 1100 and 1200 are each similar
to apparatus 500 shown in FIG. 5A, and for simplification of the
illustration, reference numerals of those elements in FIG. 10 that
are the same as in FIG. 5A are not repeated in FIG. 10, and only
those elements that differ from apparatus 500 are labeled in FIG.
10. Also, for brevity a description of the portions of apparatuses
1100 and 1200 that are the same as apparatus 500 will not be
repeated.
[0154] First apparatus 1100 includes fifth and sixth passive
devices 1120 and 1122 (e.g., receive filters for the second receive
frequency band B13_RX) each having a corresponding first device
port and a corresponding second device port, and first and second
pull down devices 1130 and 1132. The second device port of fifth
passive device 1120 is connected to the first impedance matching
device and the second device ports of first and third passive
devices 543 and 545 of apparatus 1100, and the second device port
of sixth passive device 1122 is connected to the second impedance
matching device and the second device ports of second and fourth
devices 544 and 546 of apparatus 1100. First pull down device 1130
is connected to the first impedance matching device and the second
device ports of first, third and fifth passive devices 543, 545 and
1120. Second pull down device 1132 is connected to the second
impedance matching device and the second device ports of second,
fourth and sixth passive devices 544, 546 and 1130.
[0155] In a case where a jamming or interfering signal J in the
second transmit frequency band B13_TX is received at first antenna
1005 (e.g., from second antenna 1055), then first and second pull
down devices 1130 and 1132 may reduce a voltage of the jamming or
interfering signal at the second device ports of the first, second,
third and fourth passive devices 543, 544, 545 and 546. This may
reduce one or more intermodulation products at the second apparatus
port 1103 produced from mixing of the transmit signal received at
first apparatus port 1101 and the jamming or interfering signal
J.
[0156] Similarly, second apparatus 1200 includes fifth and sixth
passive devices 1220 and 1222 (e.g., receive filters for the first
receive frequency band B5_RX) each having a corresponding first
device port and a corresponding second device port, and first and
second pull down devices 1230 and 1232. The second device port of
fifth passive device 1220 is connected to the first impedance
matching device and the second device ports of first and third
passive devices 543 and 545 of apparatus 1200, and the second
device port of sixth passive device 1222 is connected to the second
impedance matching device and the second device ports of second and
fourth devices 544 and 546 of apparatus 1200. First pull down
device 1230 is connected to the first impedance matching device and
the second device ports of first, third and fifth passive devices
543, 545 and 1220. Second pull down device 1232 is connected to the
second impedance matching device and the second device ports of
second, fourth and sixth passive devices 544, 546 and 1230.
[0157] In a case where a jamming or interfering signal J in the
first transmit frequency band B5_TX is received at second antenna
1055 (e.g., from first antenna 1005), then first and second pull
down devices 1230 and 1232 may reduce a voltage of the jamming or
interfering signal at the second device ports of the first, second,
third and fourth passive devices 543, 544, 545 and 546. This may
reduce one or more intermodulation products at the second apparatus
port 1203 produced from mixing of the transmit signal received at
first apparatus port 1201 and the jamming or interfering signal
J.
[0158] As with apparatus 500, appropriate selection of the phase
shift .theta. in first and second apparatuses 1100 and 1200 may
allow an upper or lower intermodulation product to be eliminated,
or substantially eliminated, at second apparatus ports 1103 and
1203. For example, if the phase shift .theta. is selected to be
22.5.degree. or 45.degree., an upper or lower third order
intermodulation product may be eliminated, or substantially
eliminated, at second apparatus ports 1103 and 1203.
[0159] It will be understood that in other embodiments of a
communication device, the apparatuses may include one or more of
the variations described above with respect to FIGS. 6, 7 and 9.
For example, the apparatuses may include one or more Wilkinson
devices as shown in FIG. 7 and/or one or more circulators as shown
in FIG. 9. Also, as with the embodiment shown in FIG. 6, half of
the phase shifters shown in each apparatus in FIG. 10 may be
eliminated by doubling the value of the phase shift.
[0160] In similarity to apparatuses 300 and 400, in the apparatuses
shown in FIGS. 5, 6, 7, 9 and 10, beneficially, the arrangement of
phase shifters is such that the phase shift of the transmit signal
TX through the first signal path of the first is equal or
approximately equal to the phase shift of the transmit signal TX
through the second signal path such that the TX signal is left
intact at output port of apparatus port 305.
[0161] As described above, two-port, three-port, four-port (or
more) port apparatuses may be configured to eliminate, or
substantially eliminate, an upper or lower intermodulation product
by adopting the double phase-matched configuration as described
herein with the inclusion of phase shift devices, and with an
appropriate choice of phase shift values for the phase shift
devices. For example, some embodiments may exhibit an improvement
of 20 dB or more in intermodulation performance without incurring
the severe insertion loss penalty that would typically be incurred
if a narrow passband or band reject filter was employed to reduce
the intermodulation product. Furthermore, in some embodiments a
substantial reduction in the magnitude of the intermodulation
product may be provided even in cases where the intermodulation
product is very close in frequency to a signal that is desired to
be processed by the apparatus as a transmit or receive signal. For
example, in some embodiments a substantial reduction in the
magnitude of the intermodulation product may be provided when this
separation is as little as 1 MHz at a nominal frequency of several
hundred MHz or more--something that would be difficult or
impractical with conventional filtering techniques. Finally, in
some embodiments the substantial reduction in the magnitude of the
intermodulation product may be relatively insensitive to the actual
value selected for the phase shift.
[0162] While several example embodiments of apparatuses having a
double phase-matched configuration for reducing an intermodulation
product are disclosed herein, one of ordinary skill in the art
appreciates that many variations that are in accordance with the
present teachings are possible and remain within the scope of the
appended claims. For example, although one embodiment was described
above with respect to FIG. 5B having differential device ports and
a differential apparatus port for the receive signal, it should be
understood that the other embodiments could be modified similarly
to include such differential ports. The embodiments therefore are
not to be restricted except within the scope of the appended
claims.
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